1. In a medium saucepan, combine the milk and cream with 1/2 cup of sugar. Add the lemon zest and cinnamon stick and bring to a simmer. Cover and let the mixture stand off the heat for 30 minutes.
2. Strain the milk mixture into a bowl. Set the bowl in an ice water bath and stir occasionally until chilled. Pour the milk mixture into a 9-by-13-inch glass dish.
3. In a large bowl, using an electric mixer, beat the egg whites with the remaining 2 tablespoons of sugar and the lemon juice at high speed until soft peaks form. Dollop the beaten whites all over the milk mixture and freeze until solid, about 5 hours.
4. Cut the ice milk into 2-inch squares. Using a sturdy spatula, transfer half of the squares to a food processor. Process until completely smooth, scraping down the sides of the bowl. Scrape the smooth ice milk into a bowl and freeze. Repeat with the remaining ice milk. Freeze until firm but not solid, about 30 minutes.
5. Scoop the ice milk into tall glasses and pour in the chilled espresso. Top with whipped cream and cinnamon. Serve with straws and long spoons.